THE  USE  OF  ESTER  FRACTIONS  IN  DE- 
TERMINING THE  PURITY  OF  FATS 


BY 


CARL  BECKER 


THESIS 


FOR  THE 


DEGREE  OF  BACHELOR  OF  SCIENCE 

TN 

CHEMICAL  ENGINEERING 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 


UNIVERSITY  OF  ILLINOIS 


1922 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/useofesterfractiOObeck 


/ S22 

B3S 


UNIVERSITY  OF  ILLINOIS 


__Llay__8^ i92_2._ 


THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 
Carl  Becker 


ENTITLED__Tli9__Uj3.8-jDf--EL3.tiai2-£r^c4>.i-o»it--iTi-IIai.Qrjiiinin^__tha. 

_?_?  _ 

IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 
DEGREE  OF BajchaLar — oi'--Sc.i32ac-e--in._CLi.e.Piica.l — Sn-gi^^ie-e-rA-n-e^ 


Instructor  in  Charge 


HEAD  OF  DEPARTMENT  OF 


CHEMISTRY 


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of  Contents 


I IntrocLuction. 

II  Method’ 

(si)  Conjjtints  for  Cotton  Seed 
OIX,  Linseed  Oil,  and-  Soy 
Be  An  Oil . 

(b)  Muiterition  Tests, 

III  A^psiratus  and  Details 

IV  Solutions 

V Conclusion 

VI  B1  b li  o^u  ^hy 


1. 


Ti^Use  of  Ester  Fra.ctions  in  Determining 
Tile  P.urity  of  Fats. 

I Introduction. 

It  is  obvious  that  fhere  is  an  urgent  need  for 
a short,  reliable  method  for  the  detection  of  adultei*ants 
in  fats  and  oils.  There  are  thousands  of  manufacturing 
concerns  that  use  great  quantities  of  various  fats  and  oils 
without  any  definite  information  as  to  their  purity. 

Of  course,  if  It  were  known  that  a certain  oil, 
say  olive  oil,  was  packed  and  shipped  directly  from  the 
olive  orchard,  then  it  would  be  safe  to  say  that  the  oil 
was  pure.  But  there  have  been  so  many  cases  and  types  of 
oil  and  fat  adulteration,  that  a concern  using  any  quantity 
of  oil  cugiit  to  take  avery  precaution  to  determine  its  pur- 
ity . 

At  present  the  methods  of  testing  oils  are  by 
means  of  the  Iodine  Humber,  So.pcnif ication  Humber,  Index 
of  Refraction,  and  other  similar  physical  and  chendcal 
constants,  or  by  repeated  fractional  crystallization  of 
the  acids  as  a qualitative  measure.  They  are  not  of  much 
value,  hov/ever,  because  an  oil,  by  the  use  of  two  adulter- 
ants, can  be  adulterated  so  that  it  will  e:±iiblt  the  same 
balanced  physical  and  chemical  properties  as  the  pure  oil. 
For  example,  an  oil  like  olive  oil  (Iodine  Humber  90)  can 
be  adulterated  with  two  cheap  oils,  one  having  a higher 
iodine  number  and  the  other  a lov/er  iodine  num^er  than  90  . 
By  regulating  the  proportions  in  which  they  ar®  added,  an 


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V 


2 


iodine  number  of  66-9u  can  be  obtained  which,  is  the  range 
of  iodine  numbers  of  olive  oil. 

The  index  of  refraction  varies  approximately  as 
the  iodine  number  and  molecular  weight,  that  is,  it  in- 
creases vjitn  the  degree  of  unsaturation  and  with  tne  ivom- 
ber  of  carbon  atoms  in  tne  molecule.  From  tnis  it  can  be 
seen  that  if  tne  iodine  value  of  an  oil  is  duplicated, 
txi.en  the  index  of  refraction  -.Iso  becomes  approximately 
equal  to  that  of  txie  pure  oil. 

The  saponification  numbers  oi  practically  all 
fats  and  oils  are  within  such  a close  range  tnat  they  of- 
fer very  little  evidence  <^s  to  tne  purity  of  the  fat, 
except  with  such  very  unusual  fats  as  coconut  oil  and  butter 
fat. 

Thus  it  can  be  seen  that  the  iodine  number,  sa- 
ponification number,  and  index  of  refraction,  are  of  no 
great  value  in  determining  the  nature  of  tne  adulterations 
of  a fat . 

It  was  thought  the  acids  of  tucf  fats  used  in  bal- 
ancing each  other  as  adulterants  of  a tnird  fat  may  vary 
among  themselves  in  one  of  their  constants  to  such  an  ex- 
tent, that  if  a derivative  of  the  entire  fat  may  be  obtained 
vdiich  can  be  fraction<ited,  the  acids  of  the  mixture  v/ill 
distribute  themselves  among  the  fractions  in  a fashion  diff- 
erent from  tne  acids  of  the  genuine  fat.  One  of  the  most 
important  steps  in  the  examination  of  a volatile  oil  depends 
upon  the  comparison  of  tne  constants  of  a fractionated  oil 


4 


II':  Method. 

The  esters  of  fatty  acias  may  be  prepared  from 
a fat  by  tne  method  of  Haller^,  500  grams  of  the  oil  are 
esterigled  with  1000  cc . of  absolute  methyl  alcohol  satur- 
atea  with  dry  hydrochloric  acid  gas  by  refluxing  for  twenty 
hours . The  whole  is  then  poured  over  a salt-ice  mixture 
and  stirred  vigorously.  Then  the  ester  layer  is  separated 
from  the  alcohol  and  glycerine,  shaken  v;ith  barium  carbonate 
to  remove  any  free  mineral  acid,  and  then  distilled  under 
reduced  pressure  into  five  equal  fractions.  The  Iodine  ana 
Saponification  kumoers  and  the  Indeces  of  Kei.raction  of 
these  fractions  are  then  determined  ana  compared  with  the 
constants  obtained  by  using  a similr  quantity  of  tne  pure 
oil  or  fat. 

Tables  0,4,5 ,6 ,7,  and  8 show  the  constants  that 
were  obtained  from  samples  of  pure  cotton  Seed  Oil,  Linseed 
Oil,  and  Soy  Bean  Oil, 

Tables  9,10,  11,12,13,  and  14  show  the  results 
obtained  by  using  the  adulterated  samples  as  Indicated. 

Table  15  was  obtained  from  a sample  of  crude  Soy 

Bean  Oil , 

Tables  1 and  2 were  obtu.ined  by  distilling  the 
esters  at  equal  temperature  ranges.  Fractions  were  taken 
every  4°C . 


5 


P.ure 

Cotton  Seed 

Oil 

Equal  Te 

x.perature  Ka: 

nge  Fractions 

Table  1 . 

First  j 

Kun 

Fraction 

I 

II 

III 

IV 

V 

lod.  No, 

8U  .5 

96  .2 

120.6 

136  .2 

123.0 

Sap , No . 

198  .6 

198  .5 

195  .6 

194.8 

178  .0 

Index  Ref . 

1 .4546 

1.4550 

1 .4586 

1.4629 

1.4596 

Pres,  mm. 

30.0 

- 

- 

- 

- 

Temp . ° C . 

-218 

218-22 

222-26 

226 -30 

230-35 

Table  2. 

Sec  end 

Run 

Fraction 

I 

II 

III 

IV 

V 

lod.  No. 

7B  .4 

98.7 

119  .0 

134.0 

119  .6 

Sap  .No. 

199  .8 

198  .0 

194.2 

193  .2 

175  .9 

Index  Ref. 

1.454 

1 .4569 

1 .4584 

1 .4623 

1 .4686 

Pres . mm . 

oO  .0 

- 

- 

- 

- 

T emp  . ° C . 

-218 

218 -23 

223-26 

226 -31 

231-36 

Table  3 . 

Equal  Volume 

Fractions 

First  ; 

Run 

Fraction 

I 

II 

III 

IV 

V 

lod , No . 

80  .0 

95  ,0 

110  .1 

123.5 

134  ,6 

Sap . No. 

198  .9 

195  .6 

193  .5 

190  .2 

188  .6 

Index  Ref . 

1.454 

1.457 

1.458 

1.459 

1.463 

Pres.  mm. 

26  .0 

- 

- 

- 

- - 

Temp  . ° C . 

-216 

216 -20 

220-22 

222-24 

224-31 

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Equiil  Volume  Fractions  of  Cotton  Seed  Oil--Cont 


6 


Table  4. 

Second 

Run 

Fraction 

I 

II 

III 

IV 

V 

lod  , No . 

81.0 

95  .2 

111.0 

122.9 

133.9 

Sap  . No. 

198  .0 

194.9 

193  .0 

191.3 

189  .0 

Index  Ref . 

1 .4543 

1.4571 

1.4583 

1 .4594 

1.46 

Pres  . mm. 

26  .0 

- 

- 

- 

- 

T emp  . ^ C . 

-216 

216 -20 

220-22 

222-23 

223-50 

Table  5 . 


P_ure  Soy  Bean  Oil 
Equal  Volume  Fractions 
First  Run 


Fraction 

I 

II 

III 

IV 

V 

I od  . No . 

112  .0 

124  .0 

136  .0 

144.5 

136  .3 

Sap . No. 

192  .0 

191.0 

190  .0 

189  .5 

139  .0 

Index  Ref . 

1 .4566 

1 .4585 

1 .4594 

1 .460 

1 .465 

Pre  s . mm . 

17  .0 

- 

- 

- 

- 

T emp  . ® C . 

-210 

210 -13 

213-14.5 

214  .5  -17 

217 -25 

Table  6 . 

Second 

Run 

Fraction 

I 

II 

III 

IV 

V 

lod.  No. 

113.0 

124  .7 

134.2 

143.9 

135  .6 

Sap . No . 

195  .0 

191.6 

190  .6 

190  .0 

189  .0 

Index . Ref . 

1 .4570 

1 .4588 

1 .4595 

1.4596 

1 .4648 

Pres . mm . 

17  .0 

- 

- 

- 

- 

T emp  . ® C . 

-211 

211-12 

212 -13  .5 

213  .5-18 

218 -24 

-'T  ■ 


7,. 


Pure  Linseed  Oil 
Equal  Volume  Fractions 


Table  7 . 
Fraction 

I 

First  Run 
II 

III 

IV 

V 

lod.  No. 

166  .0 

178  .0 

185  .0 

192  .1 

191.0 

Sap , No. 

195  .0 

L83  .5 

181 .5 

178  .5 

173  .0 

Index  Ref . 

1.465 

1 .4652 

1 .4665^ 

1 .4667 

1.4675 

Pres  . mn . 

14  .0 

- 

- 

- 

- 

T emp  . C . 

-209 

209 -10 

210-11 

211-12 

212-14 

Table  8 . 
Fraction 

I 

Second  Run 

II  III 

IV 

V 

lod  . No . 

166  .5 

173  .5 

184.8 

192  .4 

191.1 

Sap  . No. 

193  .6 

184.0 

132  .0 

178  .0 

173.8 

Index  Ref . 

1 .465 

1 .4653 

1 .466 

1,4869 

1 .4678 

Pres  . mm . ‘ 

14.0 

- 

- 

- 

- 

Temp . ® C . 

-208 

206-10 

210-11 

211-12 

212 -16 

Table  9 . 
Fraction 

25?  Cotton 

I 

Seed  Oil  a: 
II 

nd  75?  Linseed  Oil 
III  IV 

V 

lod  . No . 

142  .8 

157  .2 

164.4 

177  .4 

178.8 

Sap  . No. 

194  .5 

186  .0 

134.2 

180  .2 

177  .0 

Index  Ref . 

1 .46  o5 

1 .462 

1 .464 

1.465 

1.466 

Pres  . nm . 

20  .0 

- 

- 

- 

- 

Temp  C . 

-215 

215-16 

216 -17 

217-18 

218-24 

8 


5^  Gotten  Seed  Oil  and  96^  Linseed  Oil 

Table  10. 


Fraction 

I 

II 

III 

IV 

V 

lod  . Ko . 

161.8 

173.2 

178.8 

188  .2 

189  .0 

Sap  . No, 

193.9 

184.5 

182  .9 

179  .0 

174.6 

Index  Ref . 

1.4627V 

1 .4640 

1.4650 

1 .4660 

1 .4670 

Pres . mm . 

18  .0 

- 

- 

- 

- _ 

Temp C . 

-214 

214-16 

216-17? 

217 -18 

218  -25 

2^  Cotton  Seed  Oil 

and  98^  Linseed  Oil 

Table  11. 

Fraction 

I 

II 

III 

IV 

V 

lod.  No. 

16  3 .0 

175  .2 

180  .9 

190  .3 

190  .6 

Sap  .No. 

193  .7 

164  .4 

182  .9 

179  .0 

174  .6 

Index  Ref  . 

1 .4635 

1 .4647 

1 .4655 

1 .4664 

1 .4675 

Pres  . mm . 

18  .0 

- 

- 

— . 

Temp .°  C . 

-214 

214-16 

216 -18 

216-19 

219 -24 

5^  Linseed  Oil  and 

95$^  Cotton 

Seed  Oil 

Table  12. 

Fraction 

I 

II 

III 

IV 

V 

lod.  No. 

86  .0 

100.6 

116  .4 

127  .3 

137  .2 

Sap  . No . 

196  .4 

193  .1 

192  .0 

190  .2 

189  .9 

Index  Ref , 

1 .4560 

1 .4589 

1.4-596 

1 .4619, 

1.4641 

Pres  . mm . 

16  .0 

- 

— — 

— • 

Temp  C . 

-208 

208-12 

212-14 

214-15 

215 -20 

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5^  Soy 

Bean  and  95^ 

Cotton  Seed  Oil 

Table  13. 

Fraction 

I 

II 

III 

IV 

V 

I od  . No. 

63.1 

99  .8 

113  .2 

124.2 

135  .2 

Sap . No. 

198  .0 

185  .2 

194  .0 

190  .2 

189  .9 

IndeM  Ref . 

1 .4548 

1 .4576 

1.4587 

1 .4596 

1.4638 

Pre  s . mm . 

16  .0 

- 

- 

- 

- 

0 

Temp . C . 

-207 

207 -12 

212-15 

215-16 

216 -20 

• 

Cotton  Seed  Oil 

and  95^  So^' 

' Bean 

Table  14. 

Fraction 

I 

II 

III 

IV 

V 

lod  . No  . 

109  .6 

122  .1 

133.2 

141.9 

156  .0 

Sap  . No . 

192  .6 

191.9 

189  .9 

189  .5 

189  .6 

Index  Ref , 

1.4558 

1 .4560 

1 .4590 

1 .4598 

1 .4643 

Pres  . mm . 

16  .0 

- 

- 

- 

Temp  . ° C . 

-210 

210-12 

212 -15 

215  -17 

217 -23 

Crude  Soy  Bean  Oil 

Table  15. 

Fraction 

I 

II 

III 

IV 

V 

I od  . No. 

no  .3 

118  .9 

133.9 

142  .7 

137  .9 

Sap . No. 

193  .0 

190  .2 

190  .0 

189  .5 

189  .0 

Index  Ref . 

1 .4565 

1 .4582 

1 .4585 

1 .4605 

1 .4620 

Pres  . mm . 

21 .0 

- 

- 

- 

- 

Temp . ® C . 

-209 

209 -11 

211-12 

212-13 

213-31 

. ..  .1. 


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10 


Description  of  Apparatus' In.  the 
Diagram 

(1;  Jena,  Clalssen  flasK  with  an 
indented  side  neck.  1 liter. 

(«^)  Ordinary  90  cm.  condenser  tube. 

i'6j  Adapter  welded  to  ^ in.  stopcock .(4) . 

(5  Stopcock. . 

(6)  liln^  test  tube. 


W:"'  -V 


t 

i 


t' 


k =:  f;'. 

F-  ■ 


I 


« 


'I 

\ 

{ 

! 


f 

4 


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ir 


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11 


III  Apparatus  and  Details 

Cutting  the  ester  fractions  at  constant,  definite 
temperature  ranges  was  found  difficult  and  inaccurate, 
and  was  abandoned  for  the  equal  v olune -fraction  method. 

The  diagram  show  the  set-up  for  this  method. 

At  first,  the  absolute  methyl  alcohol  v;as  prepared 
by  refluxing  it  v^itii  chemico^l  lime  (8  liters  of  alcohol  to 
1600  grams  of  lime)  and  then  distilling  off  the  alcdiol. 
Then  it  was  found  that  by  using  the  ordiisary  methyl  alcohol 
with  calcium  chloride,  excellent  results  could  be  obtained. 
To  500  grams  of  oil  and  1 liter  of  alcohol,  sat’orated  with 
hydrochloric  acid  gas,  were  added  100  grams  of  anhydrous 
calcium  chloride;  this  was  then  refluxed  in  tiie  usual  way 
for  fifteen  or  twenty  hours.  Sometimes  at  the  end  of  this 
period  the  ester  layer  would  fail  to  separate,  but  by  add- 
ing 25-50  grams  more  of  calcium  chloride  and  refluxing 
for  thirty  minutes,  a perfect  separation  was  obtained. 

Before  distilling  a batch  of  esters,  the  volume 
must  be  determined  and  then  fractions  taken  so  that  the 
entire  distillate  will  be  divided  into  five  equal  parts. 
From  500  grams  of  oil  the  yield  of  esters  is  usually  about 
500  grams  having  a volume  of  about  430  cc . From  this 
volume  of  esters  about  21  cc  , are  lost  in  volatilization 
and  residue  as  a result  of  the  distillation.  This  loss  is 
appr Oyd.mately  proportional  to  the  initial  volume  of  the 
esters,  thus  making  it  easy  to  calculate  the  volume  of  the 
fractions  to  be  taken  for  any  oil. 


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12. 

Test  tubes  of  ordlnciry  glass  were  used  to  collect 
tile  fractions.  They  are  calibrated  accurately  enough  for 
this  work  by  a pencil  mark  on  a gummed  label  glued  to  the 
outside  of  the  tube, 

A pressure  of  15-20  mn.  of  mercury  was  obtained  by 
the  use  of  an  ordinary  water  suction  pi^P  • No  difficulty 
was  encountered  with  leaks.  Rubber  stoppers  were  used, 
protected  with  tin  foil.  If  leaks  occur,  they  can  be  easily 
stopped  with  a paste  of  glycerine  and  lead  oxide,  or  with 
shellac . 

Wlien  the  distillation  is  ready  to  proceed,  stopcock 
#4  is  open  and  #5  closed,  Wiien  the  desired  volume  has 
passed  over  #4  is  closed  and  #5  opened  to  release  the 
vacuum.  Then  the  test  tube  is  remo\’’ed  and  another  put  in 
place.  Then  suction  is  applied  to  #5  and  vdien  the  tube 
is  evacuated,  #5  is  closed  and  #4  opened.  In  this  way 
the  distillation  proceeds  uninterruptedly,  A Raikow 
receiver  was  used  at  first,  but  this  was  found  to  be  very 
troublesome  and  was  replaced  by  the  method  described. 


V-* 


13 


IV  Solutions  and  Determination  of  Constants 

2 

Eanus  Solution 

13.2  grams  of  iodine  and  3 cc . of  bromine  were 
dissolved  in  1 liter  of  glacial  acetic  acid,  and  kept 
in  a brown,  glass-stoppered  bottle. 

Iodine  lumbers  were  determined  as  follows:  0.250 
grams  of  tlie  oil  are  vifeighed  into  a ^lass  stoppered  flask 
and  dissolved  in  10  cc  . of  chloroform.  Then  25  cc , of 
Hanus  solution  is  added.  The  stopper  is  moistened  with 
15^  potassium  iodide  solution  and  the  groove  betv/een  the 
stopper  and  the  edge  of  the  flask,  filled  Vifith  the  same 
solution.  The  solutions  are  allowed  to  stand  for  2 hours 
in  the  dark  and  then  titrated  v;ith  sodium  thiosulfate, 
after  the  addition  of  10  cc  . of  a 15^  solution  of  potas- 
siumt  iodide  and  150  cc  . of  water. 

The  absorbtion  of  iodine  by  the  unsaturated  esters 
depends  upon  the  mass  action  law,  and  unless  a large  ex- 
cess of  iodine  is  present,  poor  results  virill  be  obtained. 
For  oils  with  Iodine  Numbers  up  t o 135,  use  25 
cc  . of  Hanus  solution  for  a 0.2500  gram  sample;  above  135, 
use  40  cc . 


Alcohol  Potash  Solution 

Dissolve  52  grams  of  potassium  hydroxide  in  a very 
small  amLOunt  of  waiter  and  filter  if  necessary.  Add  this  to 
1 liter  of  ethyl  alcohol  and  also  ^ gram  of  sodium  peroxide 
Slriake,  and  allow  to  stand  for  several  hours.  Then  filter 
and  keep  it  in  a glass  stoppered  bottle. 


14 


Saponification  iJimiticrs  v;ere  detertiined  as  follows’^: 

0 .2  y?ams  of  tiie  ester  are  weighed  into  a 250  cc  . flask 

and  dissolved  in  25  cc  . of  alcoholic  potash  solution.  The 

solution  is  the  refluxed  for  hour  and  titrated  hot  vilth 
N 

■^hydrochloric  acid,  using  phenolphthaleln  as  an  indicator. 

Cork,  and  not  rubber,  must  be  used  to  connect  the 
condenser  and  flask  for  the  refluxing,  because  the  alcohol 
dissolves  some  of  the  rubber  and  discolors  the  solution, 
masking  the  end-point. 

Sodium  Thiosulfate 
N 

Ajq  solution  of  sodium  thiosulfate  was  made  up 
and  allowed  to  stand  several  days  before  indirect  stand- 
ardization against  arsenous  oxide.  The  solution  was 
protected  with  a soda -lime  tube  against  carbon  dioxide. 

This  solution  vnus  used  for  titrating  the  excess 
Hanus  solution  in  determining  the  Iodine  numbers. 

Hydrochloric  Acid 

n 

A solution  of  hydrochloric  acid  was  made  up  and 
standardized  against  sodium  carbonate,  using  methyl  orange 
as  an  indicator, 

4 

Index  of  Refraction 

The  Indeces  of  refraction  were  determined  with  an 
Abbe  Refractometer  at  24® C , These  values  for  24°  can  be 
reduced  to  the  usual  standard  of  20®  by  using  the  factor 
0,00038  for  each  degree  Centigrade,  remembering  that  the 
refractive  index  decreases  with  an  Increase  in  temperature. 


f 4' 


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iuV-  -UA>ifu  &cJ  ni  4p-iV*i'l£>«:  I*. 

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® 'bs-*-'  . .^  »|i 

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ffi,{,,Uit^i»^  ,5Xi'fc?i.r^ien  u<»X'r  . 

i'  '■■\^t%0:£^ti^^  -iSru;  •'jv-di;^,  ct^",^’  ifto.  j.xii 

silrtft  l\  c'  **'i--,iS  J , ■ ' ■ '■> ' ■ ■ 'W  : i.  ,i 


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15 


V C one  Ivis  ions 

In  Uie  writers  opinion  tliis  iiietiioci  is  reliable  and 
can  accurately  detect  adulteration  in  fats  and  oils  as  low 
as  5^,  and  in  a goed  many  cases  as  low  as  2^. 

Tlie  detemination  of  the  Saponification  Numbers  and 
Refractive  Indices  is  not  necessary.  The  Iodine  Number  is 
sufficient  to  determine  whether  or  not  the  oil  is  pure. 

The  Saponification  Nvimber  is  not  of  much  value,  be- 
cause the  range  of  its  values  is  so  small  that  even  a ±0$ 
adulteration  would  not  cause  an  appreciable  difference  in 
the  Saponification  numbers  of  the  corresponding  fractions 
of  the  pure  and  the  adulterated  oil. 

The  Index  of  Refraction  is  also  unreliable,  because 
there  seems  to  be  other  factors,  besides  the  degree  of  un- 
saturation, and  the  number  of  carbon  atoms,  that  effect  its 
value . 

By  a study  of  the  tables  given,  it  can  be  readily 
seen  that  the  iodine  Number  immediately  reveals  ai^y  appre- 
ciable adulteration. 

The  degree  of  adul tei>ation,  of  course,  cannot  be 
determined,  but  can  be  reasonably  estimated. 

This  method  should  be  practical,  because  it  re- 
quires no  apparatus  e::cept  that  which  is  found  in  any  com- 
mercial laboratory.  The  ordinary  water  vacuum  pump  supplies 
sufficient  suction,  jt  is  not  necessary  that  the  pressure 
be  constant,  because  the  fractions  are  cut  by  volume  and 
not  temperature. 


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16 


VI  Blbiio^^rcApliy 

(1)  Compt.  rend.,  1906(143),  657. 

(2)  Zeits.  f.  Unters , d.  Nahrgai-u. 
Genuaem.,  1901,  913, 

(3)  Levskowltsch  vol.  1 p,380, 

(4)  Lewkowitsch  vol.  1 p.328. 


